As is known, an electro-optic element having a plurality of individually addressable electrodes may be employed as a multigate light valve for an electro-optic line printer. See, for example, U.S. Pat. No. 4,281,904 which issued Aug. 4, 1981 on an application of R. A. Sprague et al., for a "TIR Electro-Optic Modulator with Individually Addressable Electrodes". Also, see "Light Gates Give Data Recorder Improved Hardcopy Resolution," Electronic Design, July 19, 1979, pp. 31-32; "Polarizing Filters Plot Analog Waveforms," Machine Design, Vol. 51, No. 17, July 26, 1979, p. 62; and "Data Recorder Eliminates Problem of Linearity," Design News, Feb. 4, 1980, pp. 56-57.
Substantial progress has been made in developing multigate light valves of the foregoing type and in applying such light valves to electro-optic line printing. More particularly, a copending and commonly assigned U.S. patent application of R. A. Sprague, which was filed Sept. 17, 1980 under Ser. No. 187,911 now U.S. Pat. No. 4,389,659 on an "Electro-Optic Line Printer," shows that an image represented by a serial input data stream may be printed on a standard photosensitive recording medium through the use of a multigate light valve that is illuminated by a more or less conventional light source. That disclosure is of interest primarily because it teaches input data sample and hold techniques for minimizing the output power required of the light source. Furthermore, a copending and commonly assigned U.S. patent application of W. D. Turner, which was filed Sept. 17, 1980 under Ser. No. 187,936 now U.S. Pat. No. 4,396,252 on "Proximity Coupled Electro-Optic Devices," reveals that the electrodes and the electro-optic element of a multigate light valve may be physically distinct components which are pressed or otherwsie firmly held together to achieve "proximity coupling." Another copending and commonly assigned U.S. patent application of R. A. Sprague et al., which was filed Sept. 17, 1980 under Ser. No. 188,171 now U.S. Pat. No. 4,367,925 on "Integrated Electronics for Proximity Coupled Electro-Optic Devices," shows that it is relatively easy to make the necessary electrical connections to the many electrodes of a typical proximity coupled multigate light valve if the electrodes are fromed by suitably patterning a metallization layer of, say, a VLSI silicon electrode driver circuit. A further copending and commonly assigned U.S. patent application of W. D. Turner et al., which was filed Sept. 17, 1980 under Ser. No. 187,916 on "Differential Encoding for Fringe Field Responsive Electro-Optic Line Printers," teaches that the number of electrodes required of a multigate light valve to enable an electro-optic line printer to achieve a given resolution is reduced by a factor of two if the input data is differentially encoded. Moreover, another copending and commonly assigned U.S. patent application of R. A. Sprague et al., which was filed Mar. 30, 1981 under Ser. No. 248,939 on "Multilayer Interleaved Electrodes for Multigate Light Valves," shows that increased electro-optic efficiency and improved resolution may be obtained from a multi-gate light valve by using two or more layers of interleaved electrodes. Still another copending and commonly assigned U.S. patent application of R. A. Sprague, which was filed Mar. 30, 1981 under Ser. No. 249,057 on "Multigate Light Valve for Electro-optic Line Printers Having Non-Telecentric Imaging Systems," describes a converging electrode geometry which simplifies the imaging optics that are required to apply such a light valve to electro-optic line printing or the like. And, yet another copending and commonly assigned U.S. patent application of R. A. Sprague, which was filed Aug. 3, 1981 under Ser. No. 289,447 on "Non-Uniformity Compensation for Multigate Light Valves", provides a technique for reducing data independent variations in the optical output of a multigate light valve.
Despite the advances that have been made, prior electro-optic line printers have characteristically exhibited undesireable illumination nulls between adjacent picture elements within any given line of the printed image. Unfortunately, these nulls produce discontinuities which may materially degrade the image quality. Moreover, the straightforward techniques for eliminating the nulls, such as by defocussing or blurring the imaging system of the printer, are generally unacceptable because electro-optic line printers rely on coherent imaging.